Environmental protection has been widely accepted as a vital aspect of sustainable development. Proper sewage and septage management is a crucial parameter in achieving this. Though considerable achievement has been marked by the state in the drinking water sector, the development in sewerage sector is lagging much behind. Unplanned urbanisation and poor sewage management has resulted in large scale pollution of water resources. This has become a complex challenge to the environment as well as to the public health. Realizing the threat, the government, in recent years, has made much deliberations and initiatives to address the situation. Moreover, the Honourable National Green Tribunal (NGT) has given mandate to implement sewerage system in whole of the state in a time bound manner.

The local bodies, who have been constitutionally entrusted with the responsibility of environmental protection, have only limited infrastructure and expertise to tackle the situation. Hence Kerala Water Authority, being a state wide establishment with qualified and experienced personnel in Public Health Engineering, has been considered by the government to take up the responsibility. As per the Kerala Water Supply and Sewerage Act, 1986 KWA has the function of rendering services in collection and disposal of waste water. KWA, as a knowledge partner, service provider and central agency for coordinating the activities related to the planning and implementation of sewerage systems for LSGIs can contribute in scientific and systematic way. Hence the Authority has formulated a Sewerage Vertical within it to rise to the need of the hour. The primary task is to have a state wide plan for developing sanitation systems for the entire state. This PER deals with the same.

This Preliminary Engineering Report (PER) is prepared for seeking the necessary funds. The entire Project area is divided into appropriately sized sewerage zones based on topography, land use, population density natural features like streams and rivers and manmade features like roads and railways. The GIS software, digital elevation models (DEM) of ISRO’s Bhuvan website and DGPS survey data available with KWA are used for zoning and identifying the possible locations of STPs. The design horizon year for this project is 30 years with base year as 2023, intermediate year as 2038 and ultimate year 2053. Arithmetical or Geometrical progression method is adopted suitably for population projection.  Considering the presence of water supply schemes under KIIFB and AMRUTH a rate of supply of 100 lpcd is considered for panchayath area and 150 lpcd for urban area. A return ratio of 80% of the water supplied (including other sources viz., open well, bore wells, lorry supply, etc.) is considered for estimating the sewage generation.

The ultimate sewerage load for the state is 2827 MLD including non-domestic demand and infiltration and a total of 534 Sewerage treatment plants and 135 Septage treatment plants of total capacity 15000 KLD are proposed to cover the entire state. The proposal also includes 2439 collection wells, sewerage network of 59200 KM, manholes, collection/inspection chambers etc.  

For the purpose of planning sewerage/septage management systems, the Project area is broadly categorized into two: areas with higher population density and areas with lower population density. Networked sewerage system with STPs is proposed for the first category where the density is generally more than 1500 per square kilometre. On site sanitation with faecal sludge treatment plants are proposed for the second category areas. However sludge from non-networked areas which are closer to STPs is also planned to treat in the STP itself. The networked areas are subdivided into zones by considering topographical features such as ridges, rivers etc and manmade features such as main roads and railway lines.

This is only a preliminary report intended for seeking funds and approvals. Data available with local bodies, census reports, KWA’s asset mapping documents and spatial data sites have been used. Processing and analysis is mostly done with GIS. The accuracy of the report is limited to these.

Estimated cost is Rs. 80351 crores (excluding the amount for Thiruvananthapuram Corporation area for which DPR preparation work under RKI is already arranged) out of this Rs. 26048 crore is for urban local bodies. The unit cost per household is Rs. 1.871 lakh for networked areas and Rs. 1955 for non-networked areas.